I was looking at a Panasonic cu-80c52hp air con unit, it was reported that it has recently started to trip the rcd shortly after switching on. I disconnected the compressor and the fan runs and rest of circuitry seems ok but when compressor is re-connected it trips rcd. Is this a common fault? Any solution?
I am a gas safe engineer with electrical experience but not to familiar with air con units.
Any help greatly appreciated.

Brian_UK

10-02-2013, 12:14 AM

Unit probably shouldn't be connected through an RCD, any slight motor leakage will drop oout the breaker.

install monkey

10-02-2013, 12:17 AM

did u disconnect the compressor at the outgoing side of the contactor or at the compressor- inspect the comp termonals to prove a crimp terminal hasnt blown off,also check the overheat klixon if its external- to prove comp is goosed u need a megger- to test insulation, chances are its faulty as rcd's detect earth leakage only

Duncanbru

10-02-2013, 12:43 AM

As far as I'm aware it was originally installed on the rcd. My wife recently took over the lease on the shop unit where it is installed. I originally disconnected the capacitor from the relay to try and prove where the fault was, the unit ran without tripping. I reconnected the relay terminal and disconnected the compressor terminals, all crimps looked in tact.

install monkey

10-02-2013, 12:52 AM

you mean you disconnected the compressor-not the capacitor- can only find a spec sheet for this unit- some site wanted 15dollars for a service manual, if its inverter driven then as brian states it shouldnt be on a rcd as when the compressor stops it discharges down the neutral line, the manual stated this unit is from 1999, so could be either.
dont go ripping the rcd out , test the insulation and maybe then an rcd tester to prove the rcd isnt neusance tripping

As far as I'm aware it was originally installed on the rcd. My wife recently took over the lease on the shop unit where it is installed. I originally disconnected the capacitor from the relay to try and prove where the fault was, the unit ran without tripping. I reconnected the relay terminal and disconnected the compressor terminals, all crimps looked in tact.

Duncanbru

10-02-2013, 11:32 PM

Hi update on the Panasonic unit, my mistake it is connected through a 16a mcb not an rcd. But still have issue of breaker tripping when relay switches power to the compressor. Are the compressors available for this unit is it viable to repair or are we looking at a replacement unit.

install monkey

10-02-2013, 11:37 PM

get a clip on ammeter on it to see what it pulls on start up and compare to the name plate, should be a motor rated d type breaker, see if its a weak breaker , if its pulling lra- locked rotor amps for more than a second test the capacitor is within its uf range as stated on the cap. if all ok and it just pulls lra for a few seconds then ur pots siezed, also recommend testing the windings to earth with a megger to prove theyre over 1 meg ohm( disconnect and test each pin to earth)

Duncanbru

11-02-2013, 12:06 AM

Great thanks for advice, have a megger on loan at end of week so will get back up and test weather permitting. Will post update once tested.

monkey spanners

11-02-2013, 12:08 AM

I am a gas safe engineer with electrical experience but not to familiar with air con units.
Any help greatly appreciated.

You need to be F Gas certified to work on any refrigeration system.

Duncanbru

11-02-2013, 12:19 AM

Thanks monkey spaners, not planning to change compressor myself just narrowing down the fault. And working within my limitations. Initial thought was a seized motor or dodgy capacitor over loading the system!